Site-Specific Synthesis of Oxo-Bridged Mixed-Valence Binuclear Complexes on Mesoporous Silica

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• 作者：Akihiro Okamoto ; Ryuhei Nakamura ; Hitoshi Osawa ; Kazuhito Hashimoto
• 刊名：Langmuir
• 出版年：2008
• 出版时间：July 1, 2008
• 年：2008
• 卷：24
• 期：13
• 页码：7011 - 7017
• 全文大小：344K
• 年卷期：v.24,no.13(July 1, 2008)
• ISSN：1520-5827

文摘

We report the site-specific synthesis of mixed valence Ti^IV−O−Fe^II complexes within the pores of ordered mesoporous silica (SBA-15). By using 6-di-tert-butylpyridine as the selective activator of tripodally linked Ti^IV−OH groups of Ti-grafted SBA-15, the FeCl₂·4H₂O complexes reacted selectively with the nucleophilic Ti^IV−O⁻ groups. The formation of Si−O−Fe^II byproducts, due to the reaction with the abundant Si−OH groups, was successfully restricted and the selectivity for forming the Ti^IV−O−Fe^II complexes exceeded 80%. The metal−metal interaction of Ti^IV−O−Fe^II complexes was confirmed by the appearance of Ti^IV/Fe^II → Ti^III/Fe^III metal-to-metal charge transfer band, and their coordination, valency, and spin state were characterized by diffuse transmission UV−vis, Fourier transform IR, and Fe K-edge X-ray absorption fine structure measurements. It was also confirmed that the present methods can be extended to other metal combinations of Ti^IV−O−Ni^II and Ti^IV−O−Mn^II. The electron transfer processes occurring under photoinduced metal-to-metal charge transfer of oxo-bridged mixed valence complexes on silica supports have recently been proven as a new class of visible-light-sensitive redox centers. Thus, the present synthetic procedure allows the fabrication of a variety of photochemical reaction centers according to the molecular-level design.